1. Field of Invention
This invention relates to heat shrink tool assemblies wherein a work piece such as a drill bit or cutting tool is positioned with a tool chuck by means of heating the chuck thereby causing it to expand whereby the tool shank is inserted within the chuck and held in place by the chuck when it has cooled and shrunk around the tool shank.
2. Description of Prior Art
It is known in the art to utilize heat shrink tool assemblies in high speed industrial applications. The prior designs have utilized unitary chucks having an inner diameter slightly smaller than the exterior diameter of the shank of the cutting tool or other work piece. During use the tool chuck is heated, typically by means of induction heating, causing the chuck to expand a sufficient amount to allow the tool shank to be inserted within the chuck. The tool is then allowed to cool during which the thermal contraction of the chuck exerts a uniform pressure on the tool shank, allowing the chuck to shrink down around the tool shank to securely lock or hold the shank in place. It has long been recognized that these types of heat shrink tool assemblies provide an improvement over standard milling chucks or collet chucks.
Various prior approaches to heat shrink tool assemblies are shown in Zale, U.S. Pat. No. 2,942,891; Yamaguchi, et al., U.S. Pat. No. 5,140,739; Teeslink, U.S. Pat. No. 5,267,384, Marquert; U.S. Pat. No. 5,280,671; Kramer, et al., U.S. Pat. No. 5,277,435; Cook, U.S. Pat. No. 5,311,654 and Cook, U.S. Pat. No. 5,582,494.
These prior devices all suffer from the same shortcoming when it is desired to remove the tool from the chuck. In order to remove the tool the chuck is re-heated to expand the opening. During the heating process the chuck transfers heat to the tool shank itself. The expanding tool shank can create problems with the removal of the tool from the chuck, even resulting in the tool remaining grasped by the chuck and requiring a significant force to remove the tool.
A need therefore exists for a heat shrink tool assembly which allows for the easy and quick removal of the tool from the chuck.